Faster and better subsurface imaging for reservoir optimization
As the oil and gas market expands to meet rising demand, and the industry endeavors to sustain production levels amidst ongoing global tensions, solutions for imaging the onshore subsurface have evolved. Oil and gas expansion is particularly evident in regions such as the Middle East, which, despite an increasing focus on widening its energy mix, is committed to developing its oil and gas market.
National oil companies in the region are already on track to meet their increased targets for production in the coming years.¹ OPEC predicts that global oil demand will rise by 2.25 MMbpd in 2024 alone,² while it is expected that the market in the Middle East will grow to $1,405.7 billion by 2030, with an annual growth rate of more than 3.9%.³
This is mirrored by the increase in demand for acquiring seismic data, which is critical for new exploration projects and enhancing production from existing wells. Valued at $8.1 billion in 2023, the global seismic services market is expected to grow to a value of $14.1 billion in 2032.⁴
This predicted development in the seismic industry is not only a result of the insights it provides to the oil and gas sector, but also the wider energy market and beyond, as operators seek to secure their supply.
Seismic surveys are essential for generating a detailed understanding of subsurface structures, providing operators with the critical information needed to make informed decisions. These surveys involve specialized equipment, such as vibroseis trucks, which generate seismic energy that penetrates the earth's surface. As these seismic signals travel through the subsurface, they encounter various rock formations and reflect or refract, depending on the acoustic contrasts between different lithologic layers.
Specialist sensors, known as receivers, measure and record the seismic energy returning from the subsurface rock formations. The collected data from these receivers is then meticulously processed to create detailed images of the subsurface. Geologists analyze these images to identify and characterize geological formations to assess potential resource deposits and make informed decisions regarding drilling and exploration activities.
Technology for improved imaging, with less cost and time. The latest generation of seismic receivers are small, cable-free, autonomous seismic nodes. These modern nodes have evolved significantly from the first-generation, bulky nodal devices and the heavy, complex and expensive cabled geophone arrays of the past, Fig. 1.
In contrast to the inefficiencies and high costs of bulky nodes and cabled systems, companies can now afford to deploy more receivers on the survey area to densify the dataset and improve the subsurface image resolution to make better, more informed decisions.
These enhancements can be accomplished with lower equipment costs, fewer vehicles, minimal environmental footprint, and smaller crews. This method reduces crew exposure to health and safety risks, significantly shortens the survey timeline, and cuts operational costs by up to 50%, all while improving the quality of the subsurface image.
Having a detailed image of the subsurface is particularly crucial in regions like the Middle East, where complex geologies present significant challenges. These geologies can include faults and fractures, diverse sedimentary layers, and varying rock compositions.
For instance, the presence of salt layers and domes in some areas can distort seismic data, while fractured reservoirs require precise mapping to identify viable drilling targets. Knowing the precise positioning of these geological formations is essential for operators to determine the optimal location for a potential well, or how best to enhance recovery from existing wells. This knowledge can ultimately mean the difference between a successful drilling operation and wasted resources.
CASE STUDY
Using nodes to optimize operations and improve the subsurface image. STRYDE, a producer of the world’s smallest, lightest, and most affordable onshore receiver node, has been deployed on over 20 seismic surveys in the MENA region in the last three years.
One of these surveys was commissioned by a Middle Eastern operator, where STRYDE was engaged by seismic contractor, Africa Geophysical Services LLC (AGS), to provide high-quality 3D seismic data that will be used to make decisions related to production enhancement of a prospective field.
Despite the use of cabled equipment being the standard in the region, this forward-thinking operator was eager to use nodes for this survey for the following reasons:
- A dense 3D seismic image was necessary to obtain the level of detail required to make informed decisions related to field production enhancement and to effectively characterize the area's known complex geology of fractured and fault-bound reservoirs. It was acknowledged early on that a cabled system could not achieve the desired trace density, due to the high equipment costs associated with the equipment, therefore limiting the number of receivers that could be deployed, as well as the significant time required to initially deploy and move the equipment around the field.
- The survey was to be conducted near the operator's existing production facility and pipeline infrastructure. A cabled system would lack the necessary flexibility for deployment around the site, due to its rigidity caused by the limitations of the cable lengths, weight and bulk.
- A high-channel count of receivers was required to achieve the desired trace density across a substantial 12,000-km2 area within just two years. Therefore, a user-friendly, cost-effective, efficient, and reliable receiver system was essential to complete this survey within the planned timeframe, and within budget.
STRYDE was chosen for this survey, due to its technology's agility and capability to acquire the necessary high-trace density in a cost and time-effective manner.
With 166,000 STRYDE Nodes™ deployed on over 4.5 million receiver points (Fig. 2), this project is now recognized as the largest onshore nodal seismic survey ever acquired, to date.
The survey plan was uploaded to STRYDE’s bespoke navigation software, which utilized Real-Time Kinematic (RTK) technology to enable precise positioning, navigation, and stakeless operations. By leveraging RTK, the system provided real-time corrections and high-precision location data, ensuring that the nodes were deployed exactly according to the survey design. This approach not only streamlined the deployment process, but also reduced the potential for human error, ultimately contributing to more efficient and effective survey operations.
The software was loaded onto a handheld device and was used by a three-person deployment team, which was made up of a GPS operator, a feeder, and a node planter, who buried the receivers in 10-m intervals on lines spaced 200 m apart, resulting in an extremely dense receiver spread of 500 nodes per km.2
Each three-person deployment team (Fig. 3) planted approximately 800 nodes per day, averaging a node deployment every 20 seconds on foot. The nodes were transported to the field, using lightweight pickup trucks. The survey required 63% fewer vehicles and 65% less crew when compared to a project of the same scale using cabled receivers. These reductions significantly reduced the project's cost and exposure to HSE risk.
STRYDE’s Compact Receiver System™ (Fig. 4) was used to harvest, charge and rotate 2,140 nodes every 4 hrs for rapid re-deployment in the field. This system consists of a 20-ft shipping container housing the charging and downloading hardware, and an additional designated container for node cleaning. The system enabled the rotation of 12,960 nodes within just 24 hrs by two data managers and four operators, allowing the seismic crew to quickly roll receiver spreads with zero production downtime.
This seismic crew consisted of 203 crew members, with the most significant reduction in team size seen in the recording and maintenance team, which consisted of just 78 members, compared to the 408 people that would have been required for a project using cabled receivers. This reduction was due to the decreased equipment weight and volume of nodal equipment, and the elimination of technical downtime associated with the known failure rates of cabled systems.
The operational efficiencies realized in this survey significantly surpass what would have been achievable with a cabled system. This improvement is due to several key factors inherent to the cable-free and lightweight receiver methodology.
First, the mobility and flexibility afforded by small, cableless technology eliminated the physical constraints and logistical challenges associated with cables or bulky nodes. This led to faster setup times, easier relocation of equipment, and reduced labor costs.
Additionally, the use of this cableless system enhanced data collection accuracy and reliability by eliminating the risk of cable damage or signal interference, and technical downtime associated with fixing cable breaks. The streamlined operations not only expedited the survey process, but also enhanced overall productivity and data quality.
Seismic data QC and image reconstruction. With the project still being operational, a staggering 20-30 terabytes of data are continuously acquired every day by STRYDE’s nodes. This immense volume of data underscores the scale and complexity of the undertaking.
To ensure the highest quality, the seismic crew used STRYDE custom-designed software for rapid in-field quality control (QC) of both the recorded data and the source positioning, quality and timing data. This specialized software streamlines the QC process, allowing for efficient and thorough validation of the data on-site.
Once the data have been meticulously checked and verified, they are then exported to Network-Attached Storage (NAS) drives, with duplicates created to ensure data integrity and redundancy.
Following this, the data undergo a secure and systematic transfer onto seismic tapes. These tapes are specially designed to handle large volumes of seismic data, offering a robust and reliable medium for long-term storage and archival, providing a dependable solution for preserving the vast amounts of data generated by the survey.
After being stored securely on seismic tapes, the data are ready for the next crucial stage, seismic image construction. The processing begins with the transfer of data from the seismic tapes to high-performance computing systems equipped with advanced seismic processing software. This software is designed to handle the extensive data sets and complex algorithms required for seismic imaging.
The first step in processing involves data conditioning, which includes noise reduction, signal enhancement, and correction for any data inconsistencies. This ensures the raw data are of the highest quality before further analysis. Following this, the data undergo a series of sophisticated processing techniques:
- Velocity analysis: This step involves estimating the seismic wave velocities through the subsurface layers, which is critical for accurate depth imaging.
- Migration: Using the velocity model, the seismic data are then migrated. Migration repositions the recorded seismic events to their correct locations in the subsurface, creating a clearer and more accurate image of the geological structures.
- Stacking: Multiple seismic records from different nodes and times are combined to enhance signal quality and suppress noise, resulting in a more coherent seismic image.
- Inversion: This technique converts seismic reflection data into a quantitative rock property model, providing detailed information about the subsurface materials.
- Attribute analysis: Seismic attributes, such as amplitude, phase, and frequency, are extracted and analyzed to further interpret the subsurface features.
Throughout this process, continuous QC checks ensure the accuracy and reliability of the seismic image. After the initial data processing steps, advanced techniques, such as Full Waveform Inversion (FWI) and high-resolution tomography, were applied to further refine the seismic image and enhance subsurface characterization.
The final product is a high-resolution seismic image that provides valuable insights into subsurface geology.
The future of faster and better imaging of the subsurface. As the oil and gas industry continues to seek greater efficiencies to meet ongoing demand, the importance of technologies that enhance operational performance and image quality during the exploration phase has never been more critical. STRYDE's agile nodes play a pivotal role in this landscape by enabling the acquisition of high-density data quickly and at an affordable price point.
In an increasingly volatile market environment, such technologies provide a crucial layer of confidence. They provide the opportunity to help operators mitigate risks and adapt to market fluctuations with greater agility. These nodes facilitate the acquisition of the high-density data needed for these purposes, making advanced geophysical surveys both feasible and economically viable.
REFERENCES
- https://www.eia.gov/todayinenergy/detail.php?id=61365
- https://www.reuters.com/markets/commodities/oil-prices-head-back-up-middle-east-jitters-2024-04-12/
- https://www.globenewswire.com/en/news-release/2023/10/04/2754445/0/en/Middle-East-Oil-Gas-Market-Report-Market-Size-Share-Consumption-Production-Historical-and-Forecast-Data-2019-2030.html
- https://www.gminsights.com/industry-analysis/seismic-services-market#:~:text=Seismic%20Services%20Market%20size%20was,6.3%25%20between%202024%20and%202032.
